It is generally known in the art to provide a web cassette for holding and dispensing a roll of unexposed light-sensitive web material for use in phototypesetting apparatus, in semi-automatic process cameras, for instance, for handling diffusion transfer material in a daylight environment, etc. In such web cassettes, the end caps have peripheral slots for receiving side edges of the cassette jacket, and are secured in light-tight relation to the side edges by adhesive and/or staples. Accordingly, a shortcoming of the prior art web cassettes is that the assembly steps of applying the adhesive to the side edges of the jacket and stapling together the mating edges of the end caps and jacket side edges add to the cost of manufacturing the web cassettes.
One prior art attempt to solve the aforementioned problem includes U.S. Pat. No. 4,903,833 which teaches a cartridge for light sensitive web-type material having inwardly extending annular rings in the housing ends which terminate in close running relation to the adjacent outside surface of a spool end flange to support the media material and to prevent telescoping in the event the cartridge or cassette is mishandled or dropped. While the cartridge therein disclosed may have sufficed for its intended purpose, it does not fulfill the present need set forth hereinabove.
Moreover, in various cassettes now in use for webs of photosensitive film and paper, the web is wound on a spool or core, with or without flanges, and is disposed within a cassette which totally surrounds the web and protects it from light and other damaging effects. One end of the web is normally secured to the core or spool center, and the other end extends out of the cassette through an exit slot therein. The other end of the web is fastened to the surface of the cassette, and is released therefrom for insertion into a camera or the like. It has been found that there is a tendency for the web in such cassettes to unwind during handling and shipping. Inasmuch as the inner end of the web is connected to the core or the spool center, and the other end is normally secured to the outer surface of the cassette, the web acts as a released clockspring, turning the spool as it unwinds. Such web clockspringing can result in scratching of the surface of adjacent web convolutions, causing a deterioration in the quality of the image that may be recorded thereon. In other instances the web can clockspring outwardly to the extent that the outer convolution of web jams against the inner surface of the cassette, making subsequent unreeling of the web difficult or impossible. In those situations in which the outer end of the web is not fastened to the surface of the cassette or is inadvertently released from the cassette surface, the clockspringing can cause the outer end of the web to be pulled back through the slot into the cassette, resulting in a cartridge that is completely unusable.
Various attempts have been made to provide a method of preventing clockspringing, i.e, unwinding of the web in cassettes. For example, one such method using a core locking device for a web dispensing cassette is disclosed and published as Item No. 16352 in the November 1977 issue of Research Disclosure. In this core-locking device, the web winding core is provided with a slotted end, and a core-locking member is provided that is captive and slidable in one of the two end caps of the cassette. In U.S. Pat. No. 3,831,881, an anti-backup device is disclosed comprising a fork-like member located within a hollow core on a rotatable film take-up core. The control member has flexible outwardly extending arms projecting from a body portion. In an engaged position of the control member, the arms thereof slide over internal cam or ratchet surfaces of the take-up core during rotation of the core in the forward (take-up) direction, and hence permits such rotation. On the other hand, these arms engage the cam or ratchet surfaces of the core post to block rotation of the core when an attempt is made to rotate the core in the reverse (unwinding) direction. When the film cartridge is placed within a camera, the fork-like member can be moved axially until it is out of engagement with the camera ratchet surfaces, thereby permitting free rotation of the core in both the forward and reverse directions. In U.S. Pat. No. 4,756,418, an anticlockspringing apparatus is disclosed comprising a clip separate from the core and cassette, having opposite ends thereof insertable through aligned notches and slots in the core and cassette respectively, for locking the core to the cassette.
Therefore a need exists for a light tight web cassette that is easy to assemble and economical to manufacture and, an improved anti-clockspring method for preventing unwinding of the web in the cassette thereby reducing incidences of damaged cartridges.